Mass spectral data acquired using a mass spectrometer, such as a Time of Flight (“ToF”) mass spectrometer, can suffer from undesirable peak skirting or baseline rising. This can be due, for example, to incomplete desolvation of the Liquid Chromatography (“LC”) eluent supplied to the mass spectrometer or to ions colliding with residual gas in the mass analyser.
Collisions of ions with gas in the mass analyser can cause ions to fragment and release energy thereby causing either an acceleration or deceleration of the product ions. If this occurs, for example, in the field free region of a reflectron Time of Flight (“ToF”) mass analyser or in a linear Time of Flight (“ToF”) mass analyser then the ion peak widths are increased and undesirable peak skirts are produced in the resulting mass spectral data. The degree to which these effects occur depends on the ratio of the number of ions that collide during their time of flight (which is a function of their collisional cross section and the background pressure) to the number of ions that do not collide, as well as the energy released during the collision process (known as the “Derrick Shift”) which causes product ions to change speed relative to their corresponding parent or precursor ion.
Kast et al., “Noise Filtering Techniques for Electrospray Quadrupole Time of Flight Mass Spectra”, J. Am. Soc. Mass Spectrom. 2003, 14, 766-776 discloses removing periodically repeating chemical background noise peaks from Time of Flight (“ToF”) mass spectral data by manually selecting and eliminating individual peaks in the Fourier spectrum of the mass-to-charge ratio (“m/z”) domain data. However, this approach does not address the problem of undesirable peak skirting effects.
It is therefore desired to provide an improved method of mass spectrometry.